Image forming apparatus

ABSTRACT

In accordance with an embodiment, an image forming apparatus comprises a paper feed cassette configured to be capable of stacking and housing an envelope; a pickup roller configured to pick up the envelope from the paper feed cassette; a paper feed roller pair configured in a direction orthogonal to the conveyance direction of the envelope picked up by the pickup roller to convey the envelope with nipping the center area of the envelope; and a pressing roller pair configured in a direction orthogonal to the conveyance direction of the paper feed roller pair adjacent to the paper feed roller pair to convey the envelope with nipping the flap of the envelope, wherein the conveyance force applied to the envelope by the pressing roller pair is weaker than the conveyance force applied to the envelope by the paper feed roller pair.

FIELD

Embodiments described herein relate generally to an image forming apparatus capable of feeding an envelope.

BACKGROUND

Conventionally, in an image forming apparatus, a paper taken out from a paper feed cassette is conveyed to an image forming section to form an image on the paper. Further, a pickup roller for picking up paper is arranged in the paper feed cassette. Further, a paper feed roller is arranged nearby the pickup roller.

Incidentally, the image forming apparatus feeds an envelope from the paper feed cassette. In a case in which the envelope is fed from the paper feed cassette in a longitudinal direction, the flap of the envelope may open. Further, the rigidity of the part where there is the flap becomes strong. Thus, if the conveyance path is bent, there is a possibility that the conveyance of envelope stalls and a jam occurs.

In the past, there is an apparatus in which a pressing member is arranged in a paper feed tray to press the center part of the envelope. The pressing member rectifies the bulge of the envelope. However, to suppress the opening of the flap of the envelope is limited in the paper feed tray. Thus, the flap may open in the conveyance path after the envelope is fed even if the envelope is pressed just before being fed. Further, if the pressing force of the pressing member is weak, there is a disadvantage that the flap opens at a downstream position of the paper feed roller during the conveying, and the envelope is conveyed while the rigidity thereof is strong.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the constitution of an image forming apparatus according to an embodiment;

FIG. 2 is a diagram illustrating the constitution of a paper pickup section according to the embodiment;

FIG. 3 is a perspective view illustrating a paper feed cassette and the paper pickup section according to the embodiment;

FIG. 4 is a plan view illustrating the paper pickup section when viewed from above according to the embodiment; and

FIG. 5 is a perspective view illustrating a modification of the paper pickup section according to the embodiment.

DETAILED DESCRIPTION

In accordance with an embodiment, an image forming apparatus comprises:

a paper feed cassette configured to be capable of stacking and housing an envelope with a flap;

a pickup roller configured to pick up the envelope from the paper feed cassette;

a paper feed roller pair configured in a direction orthogonal to the conveyance direction of the envelope picked up by the pickup roller to convey the envelope with nipping the center area of the envelope; and

a pressing roller pair configured in a direction orthogonal to the conveyance direction of the paper feed roller pair adjacent to the paper feed roller pair to convey the envelope with nipping the flap of the envelope, wherein the conveyance force applied to the envelope by the pressing roller pair is weaker than the conveyance force applied to the envelope by the paper feed roller pair.

Hereinafter, the image forming apparatus according to the embodiment is described in detail with reference to the accompanying drawings. Further, same components are applied with the same reference numerals in the drawings, and therefore the description thereof is not provided.

(A first Embodiment)

FIG. 1 is a diagram illustrating the constitution of an image forming apparatus according to the embodiment. In FIG. 1, an image forming apparatus 100 is an electrophotographic type copier. In addition to the copier, a printer, a multi-function peripheral (MFP) and the like may also be used as the image forming apparatus 100. The copier is exemplified in the following description.

The image forming apparatus (copier) 100 is provided with a printer section 10 at the center thereof . The printer section includes a rotatable photoconductive drum 11. The photoconductive drum 11 serving as an image carrier includes an organic photo conductor (OPC) at the outer peripheral surface thereof. If the photoconductive drum 11 is irradiated with light in a state of being applied with a given potential, the potential of the area of the photoconductive drum 11 irradiated with the light is changed. The photoconductive drum 11 maintains the change of the potential as an electrostatic latent image for a given time.

An electrostatic charger 12, an exposure unit 13, a developing device 14, a transfer roller 15, a drum cleaner 16 and a charge removing LED 17 are arranged around the photoconductive drum 11 along a rotation direction T of the photoconductive drum 11.

The electrostatic charger 12 charges the surface of the photoconductive drum 11 to a given potential. The exposure unit 13 irradiates the photoconductive drum 11 with a laser beam LB to expose the photoconductive drum 11. Through the exposure processing, the electrostatic latent image is formed on the surface of the photoconductive drum 11. The light intensity of the laser beam LB varies according to image density and the like .

The developing device 14 stores two-component developing agent including toner and carrier. The developing device 14 supplies developing agent to the surface of the photoconductive drum 11 to develop the electrostatic latent image on the photoconductive drum 11. The electrostatic latent image on the surface of the photoconductive drum 11 is visualized to form a toner image. The transfer roller 15 applies a given potential to a paper S serving as an image receiving medium. The transfer roller 15 transfers the toner image on the photoconductive drum 11 to the paper S. The transfer roller 15 constitutes a transfer device.

The drum cleaner 16 removes and collects the toner left on the surface of the photoconductive drum 11. The charge removing LED 17 removes the charge left on the photoconductive drum 11. Further, a fixing device 19 is arranged at the downstream side of the transfer roller 15. The fixing device 19 conveys the paper S, and meanwhile heats and presses the paper S at a given temperature. The toner image is fixed on the paper S by the fixing device 19.

Further, a developing agent cartridge 18 for housing toner and developing agent is arranged above the developing device 14. After the toner and the developing agent in the developing device 14 are consumed, the toner and the developing agent are supplied from the developing agent cartridge 18 to the developing device 14.

Further, a scanner section 20 is arranged at the upper portion of the image forming apparatus 100. The scanner section 20 includes a light source 22, a reflecting mirror 23 and an image sensor 24. The light source 22 irradiates the document placed on a document placing table 21 with light. The reflecting mirror 23 reflects the light reflected from the document. The image sensor 24 receives the light reflected from the reflecting mirror 23.

Further, a document cover 25 is arranged at the upper portion of the document placing table 21 in an openable manner. Further, an operation panel 26 is arranged nearby the scanner section 20. The operation panel 26 includes a touch panel type display section 27 and operation keys 28.

Further, a paper feed cassette 31 is arranged at the lower portion of the image forming apparatus 100. A plurality of paper feed cassettes 31 may be arranged according to the paper size or paper type. For example, the paper feed cassette 31 may be constituted by two parts, the upper part thereof is used to house normal paper, and the lower part thereof is used to store envelopes.

The paper S in the paper feed cassette 31 is picked up by a pickup roller 41. The picked up paper S is guided to the transfer roller 15 by a conveyance roller 32 and a register roller 33. The pickup roller 41 picks up the paper S in the paper feed cassette 31 one by one. The conveyance roller 32 rotates at given timing to align the positions of the paper S and the toner image formed on the photoconductive drum 11. Through the rotation of the conveyance roller 32, the paper S is conveyed to the transfer roller 15. The paper S passing through the transfer roller 15 is conveyed to the fixing device 19. The paper S passing through the fixing device 19 is discharged to a paper discharge tray 36 by a paper discharge roller 35.

In a case of simplex printing, the paper S is conveyed through a conveyance path 37. The paper S is conveyed from the register roller 33 to the transfer roller 15. Further, the paper S is conveyed from the transfer roller 15 to the paper discharge roller 35 via the fixing device 19.

Further, a reversal conveyance path 38 is arranged, independent from the conveyance path 37, to be used in a case of duplex printing. In a case of duplex printing, the paper S is temporarily conveyed from the paper discharge roller 35 towards the paper discharge tray 36. Then the paper S is switched back and conveyed to the reversal conveyance path 38. The reversal conveyance path 38, which is provided with a plurality of conveyance rollers, reverses and guides the paper S to the register roller 33.

When forming an image, the document on the document placing table 21 is irradiated with the light from the light source 22. The light reflected from the document is reflected by the reflecting mirror 23 to the image sensor 24, in this way, the document image is read by the image sensor 24. The laser beam LB is output from the exposure unit 13 based on the information read by the image sensor 24, or the image information supplied from an external device such as a PC (Personal Computer) and the like. The surface of the photoconductive drum 11 is irradiated with the laser beam LB. The surface of the photoconductive drum 11 is charged to negative polarity by the electrostatic charger 12. The photoconductive drum 11 is exposed by emitting the laser beam LB from the exposure unit 13. In this way, the electrostatic latent image is formed on the surface of the photoconductive drum 11.

If the paper S taken out from the paper feed cassette 31 is conveyed to the transfer roller 15, the toner image on the photoconductive drum 11 is transferred to the paper S by the transfer roller 15. The paper S to which the toner image is transferred is conveyed to the fixing device 19. The paper S is heated and pressed by the fixing device 19 to fix the image on the paper S. The paper S on which the image is fixed is discharged to the paper discharge tray 36 through the paper discharge roller 35.

FIG. 2 is a diagram illustrating the constitution of a paper pickup section 40 for picking up a paper from the paper feed cassette 31. In the following example, a case in which an envelope E is housed in the paper feed cassette 31 is exemplified. FIG. 3 is a perspective view illustrating the paper feed cassette 31 in which the envelope E is housed and the paper pickup section 40.

As shown in FIG. 2 and FIG. 3, the paper pickup section 40 includes the pickup roller 41 for picking up a paper from the paper feed cassette 31. The pickup roller 41 is mounted on a rotary shaft 42. Further, the paper pickup section 40 includes a pair of paper feed rollers 43 and 44. The paper feed rollers 43 and 44 convey the paper taken out by the pickup roller 41. The paper feed roller 43 is mounted on a rotary shaft 47. The paper feed roller 44 is mounted on a rotary shaft 48. The rotary shafts 47 and 48 are arranged to be parallel to each other in a direction orthogonal to the conveyance direction of the envelope E.

The pickup roller 41 rotates in a state of being contacted with the center area of the envelope E in the paper feed cassette 31. The envelope E in the paper feed cassette 31 is picked up by the pickup roller 41 one by one. The envelope E picked up by the pickup roller 41 is sent to the paper feed rollers 43 and 44. When a plurality of envelopes E is picked up by the pickup roller 41, the paper feed roller 44 separates only one envelope E to feed it to the subsequent stage. The paper feed roller 44 is also referred to as a separation roller.

The pair of the paper feed rollers 43 and 44 is arranged opposite to each other. The envelope E picked up by the pickup roller 41 is nipped by the paper feed rollers 43 and 44 and then conveyed to the conveyance roller 32 through the rotation of the paper feed rollers 43 and 44.

Further, a pair of pressing rollers 45 and 46 at the rear side in figures is respectively arranged on the rotary shafts 47 and 48 adjacent to the paper feed rollers 43 and 44. The pressing rollers 45 and 46 are used to press the flap F of the envelope E. The pressing rollers 45 and 46 are mounted on the rotary shafts 47 and 48 at positions corresponding to the flap F.

The rotary shaft 42 is rotated by a motor 51, and the rotary shaft 48 is rotated by a motor 52. If the paper feed roller 44 rotates along with the rotation of the rotary shaft 48, the paper feed roller 43 rotates and the rotary shaft 47 also rotates. That is, if the rotary shaft 48 rotates, the rotary shaft 47 is driven to rotate.

The rotary shaft 42 rotates by the motor 51 in a direction in which the envelope E is conveyed. Similarly, the rotary shafts 47 and 48 rotate by the motor 52 in directions in which the envelope E is conveyed. Further, the rotary shaft 47 may be rotated by the motor 52, and the rotary shaft 48 is driven to rotate. Further, as shown in FIG. 2, guides 49 are arranged at the downstream side of the paper feed rollers 43 and 44 and the pressing rollers 45 and 46 to support the conveyance of paper.

On the other hand, the paper feed cassette 31 includes an L-shaped cassette main body 61, a tray 62, side plates 631 and 632, and a rear plate 64. A plurality of envelopes E is stacked in the tray 62. The side plates 631 and 632 regulate and align the two sides of the envelope E. The rear plate 64 regulates the rear end of the envelope E.

Further, a spring 65 for lifting and lowering a sheet is arranged between the cassette main body 61 and the tray 62. The tray 62 is energized upward by the spring 65. Thus, the envelope E stacked at the top of the tray 62 is contacted with the pickup roller 41.

FIG. 4 is a plan view illustrating the paper pickup section 40 when viewed from above. The pickup roller 41 is positioned near the center of the front end in the feed direction (indicated by an arrow X) of the envelope E. When the pickup roller 41 rotates, the envelope E is picked up from the paper feed cassette 31. The envelope E picked up by the pickup roller 41 is sent to the paper feed rollers 43 and 44 and the pressing rollers 45 and 46.

As shown in FIG. 4, the diameter of the paper feed rollers 43 and 44 is D1. Further, the diameter of the pressing rollers 45 and 46 is D2. The diameter D2 of the pressing rollers 45 and 46 is slightly smaller than the diameter D1 of the paper feed rollers 43 and 44, that is, D1>D2.

In the embodiment, the pressing roller 45 is mounted on the same rotary shaft 47 as the paper feed roller 43. The paper feed roller 43 and the pressing roller 45 are rotated and stopped synchronously. Further, the pressing roller 46 is mounted on the same rotary shaft 48 as the paper feed roller 44. The paper feed roller 44 and the pressing roller 46 are rotated and stopped by the motor 52 synchronously. That is, in order to convey the envelope E, the rotary shafts 47 and 48 are rotated in opposite directions, and rotated and stopped synchronously. Further, a one-way clutch is equipped on the pressing roller 46 (driving-side roller) of the pressing rollers 45 and 46 to carry out the feeding and conveying operations in synchronization with the paper feed roller 44. Thus, the motor 52 serves as a driving source for synchronously rotating the paper feed rollers 43 and 44 and the pressing rollers 45 and 46 respectively.

Further, the conveyance force applied to the envelope E by the pressing rollers 45 and 46 is smaller than the conveyance force applied by the paper feed rollers 43 and 44. That is, as stated above, by setting the diameter D1 of the paper feed rollers 43 and 44 and the diameter D2 of the pressing rollers 45 and 46 to meet the following relation: D1>D2, the conveyance force applied to the envelope E by the pressing rollers 45 and 46 is reduced.

Since the envelope E has the flap F, the thickness thereof at the side of the flap F is increased. Thus, the conveyance force is reduced by weakening the force used to nip the envelope E by the pressing rollers 45 and 46. Even if the conveyance force is reduced, the force used to nip the center area of the envelope E is almost equivalent to the force used to nip the flap F because the side where there is the flap F is thick. In this way, the envelope E is conveyed with equal conveyance force in the center area and the part of the flap F. The envelope E is conveyed with equal conveyance force in the center area and the part of the flap F of the envelope E, thereby preventing the skew of the envelope E.

If the flap F of the envelope E opens, the rigidity of the envelope E becomes strong. When the rigidity of the envelope E becomes strong, the conveyance resistance is increased at the curved part of the guides 49. If the conveyance resistance is increased, the envelope E cannot be conveyed smoothly and a jam may occur.

In the embodiment, the bulge or the opening of the flap F of the envelope E can be prevented through the pair of the pressing rollers 45 and 46. After passing through the paper feed rollers 43 and 44, the envelope E is conveyed along the curved guides 49. By preventing the bulge or the opening of the flap F, the rigidity of the envelope E is weakened and the envelope E can be conveyed smoothly when it is passed through the curved part of the guides 49. As a result, it is possible to reduce the occurrence of a jam.

Further, in the example described above, since the conveyance force applied by the pressing rollers 45 and 46 is smaller than the conveyance force applied by the paper feed rollers 43 and 44, the diameter of rollers is set to meet the following relation: (D1>D2). However, in addition to selecting the diameter of rollers, the friction coefficient of the pressing rollers 45 and 46 may be smaller than the friction coefficient of the paper feed rollers 43 and 44. That is, the pressing rollers 45 and 46 and the paper feed rollers 43 and 44 may use materials having different friction coefficient.

FIG. 5 is a perspective view illustrating a modification of the paper pickup section 40 according to the embodiment.

The orientation of the envelope E housed in the paper feed cassette 31 is different from that in FIG. 3. The flap F of the envelope E is positioned at the side of the side plate 631 in FIG. 3, while the flap F of the envelope E is positioned at the side of the side plate 632 in FIG. 5.

Thus, the pair of the pressing rollers 45 and 46 is arranged at positions corresponding to the flap F of the envelope E. That is, the pair of the pressing rollers 45 and 46 arranged at the nearer side on the rotary shafts 47 and 48 is adjacent to the pair of the paper feed rollers 43 and 44.

In FIG. 5, the bulge or the opening of the flap F of the envelope E can be prevented through the pressing rollers 45 and 46. The rigidity of the envelope E is weakened by the pressing rollers 45 and 46 and the envelope E can be conveyed smoothly. As a result, it is possible to reduce the occurrence of a jam.

Further, it is exemplified in FIG. 3 and FIG. 5 that the envelope E is housed in the paper feed cassette 31, and the normal paper may also be housed. In a case in which the normal paper is housed, the center area of the normal paper is conveyed by the paper feed rollers 43 and 44. Since the conveyance force of the pressing rollers 45 and 46 is weaker than the conveyance force of the paper feed rollers 43 and 44, the normal paper is mainly conveyed by the paper feed rollers 43 and 44. Thus, it is possible to convey the normal paper, and meanwhile reduce the occurrence of a jam.

In accordance with the image forming apparatus according to the embodiment described above, in a case in which the envelope E is housed in the paper feed cassette 31, the bulge or the opening of the flap F of the envelope E can be prevented by the pressing rollers 45 and 46 when the envelope E is being conveyed, thereby reducing the occurrence of a jam.

Further, the present invention is not limited to the embodiment described above, and various applications are possible. For example, the present invention may be applied to a quadruple tandem image forming apparatus provided with a plurality of developing units for different colors. Further, a scanning head including LED elements may be used instead of the exposure unit 13 including the laser light source.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention. 

1. An image forming apparatus, comprising: a paper feed cassette configured to be capable of stacking and housing an envelope with a flap; a pickup roller configured to pick up the envelope from the paper feed cassette; a paper feed roller pair configured in a direction orthogonal to the conveyance direction of the envelope picked up by the pickup roller to convey the envelope with nipping the envelope; and a pressing roller pair configured in a direction orthogonal to the conveyance direction of the paper feed roller pair adjacent to the paper feed roller pair to convey the envelope with nipping the flap of the envelope, the diameter of the pressing rollers is also set to be smaller than the diameter of the paper feed rollers.
 2. The apparatus of claim 1, the paper feed roller pair is mounted on rotary shafts that are arranged to be parallel to each other in a direction orthogonal to the conveyance direction of the envelope picked up by the pickup roller; and the pressing roller pair is arranged at a position corresponding to the flap on the rotary shafts adjacent to the paper feed roller pair.
 3. The apparatus of claim 1, since the conveyance force applied to the envelope by the pressing rollers is smaller than the conveyance force applied by the paper feed rollers, the force used to nip the envelope by the pressing rollers is also set to be smaller than the force used to nip the envelope by the paper feed rollers.
 4. (canceled)
 5. The apparatus of claim 1, the paper feed rollers include a separation roller for separating only one envelope to feed it to the subsequent stage when a plurality of envelopes is picked up by the pickup roller.
 6. The apparatus of claim 1, further comprising: a driving source configured to drive each of the paper feed rollers and the pressing rollers to rotate and stop synchronously.
 7. An image forming apparatus, comprising: a paper feed cassette capable of housing an envelope with a flap; a pickup roller configured to pick up the envelope from the paper feed cassette; paper feed rollers configured to be respectively mounted on rotary shafts that are arranged to be parallel to each other in a direction orthogonal to the conveyance direction of the envelope picked up by the pickup roller to convey the envelope to a subsequent stage with nipping the envelope; pressing rollers configured to be respectively mounted on the rotary shafts adjacent to the paper feed rollers to convey the envelope with nipping the flap of the envelope, the diameter of the pressing rollers is also set to be smaller than the diameter of the paper feed rollers; a conveyance roller configured to convey the envelope conveyed by the paper feed rollers and the pressing rollers to a transfer device; and a fixing device configured to fix an image transferred by the transfer device on the envelope.
 8. The apparatus of claim 7, since the conveyance force applied to the envelope by the pressing rollers is smaller than the conveyance force applied by the paper feed rollers, the force used to nip the envelope by the pressing rollers is also set to be smaller than the force used to nip the envelope by the paper feed rollers.
 9. (canceled)
 10. The apparatus of claim 7, further comprising: a driving source configured to drive each of the paper feed rollers and the pressing rollers to rotate and stop synchronously.
 11. The apparatus of claim 7, the pressing rollers and the paper feed rollers use materials having different friction coefficients. 